Red eye removal in photographs is well known in the patent literature. The following U.S. patents are believed to represent the current state of the art:
4,285,588August 1981Mir396/1584,315,204February 1982Abelson514/4004,978,989December 1990Nakano et al.396/0885,130,789July 1992Dobbs et al.358/5005,748,764May 1998Benati et al.382/1175,990,901November 1999Lawton et al.345/4295,990,973November 1999Sakamoto348/5766,009,209December 1999Acker et al.382/2756,016,354January 2000Lin et al.382/117
When photographs are taken of people using a digital or traditional film camera with a flash, a common artifact that can appear in the picture is referred to as “red eye.” This artifact manifests itself as a red coloration within the iris of an eye, instead of the natural eye color, and is referred to as a “flash effect.”
Red eye is caused by the reflection of light from a flash off of the blood vessels of the retinas of a subject's eyes. The size of the area affected by red eye increases with increased dilation of the eye.
One can try to reduce the red eye effect by increasing the light level in a room. Alternatively, one can have a subject look at a bright light, such as a room lamp, just before taking the flash picture. Both methods of red eye reduction described above cause the pupils of the subject's eyes to contract, thereby reducing the amount of reflective surface.
Reference is made to FIG. 1, which is a simplified line drawing showing a typical red eye artifact in a photograph. An area 110 corresponding to the iris of an eye, of blue coloration, encompasses a pupil area 120 that exhibits redness. Within area 120 there is seen a small white flash area 130, which represents reflections of white light from the flash. Were it not for the red eye artifact, area 120 would appear similar in color to area 110, being part of the iris. Instead, the artifact gives it a red appearance.
Interestingly, this flash effect appears as red eye in humans, but as yellow eye in dogs and cats, and as green eye in some other animals. Photographers and image compositors commonly touch up their images and remove red eye flash effects from eyes.
Adobe Systems Inc.'s PHOTODELUXE® and Microsoft Corporation's PICTURE IT!® are digital photo-editing software applications that offer semi-automatic red eye removal as a feature.